1. Field of the Invention
The present invention relates to a positioning mechanism, and more particularly to a precise and rapid positioning mechanism which is used to align accurately a mesh of a stencil to a surface mounting position on a printed circuit board.
2. Description of the Prior Art
In applying conventional surface mount technology (SMT) to stencil printing using solder paste, it depends a lot on an operator""s highly sensitive visibility and skillful aligning technique so that a mesh on a stencil can be aligned to a corresponding soldering point on the printed circuit board placed on a carrier for achieving the object of positioning. Moreover, the above described positioning technique further influences both quality of soldering and yield of the product.
In addition to employing the above mentioned method for carrying out the work by experienced operator skillfully with his/her naked eyes, an auxiliary vision system apparatus may be employed to aid the aligning work. However, the object of precise aligning may be achieved with the aid of additional investment of software, hardwares and servo system. As a result, the entire equipment becomes more complicated and the cost is increased as well.
In order to solve the above described problems, the present inventors carried out theoretical studies and simulating experiments. Based on these studies and researches, the present inventors came to propose the present invention.
It is an object of the present invention to provide a precise and rapid positioning mechanism which can perform printing of a printed circuit board more effectively, accurately and efficiently without need of experienced operators.
It is another object of the present invention to provide a precise and rapid positioning mechanism which, in comparison with a conventional one, is added a movable positioning pin mechanism and two setting holes provided on both the stencil and the carrier for improving the working efficiency and upgrading accuracy.
It is still another object of the present invention to provide a precise and rapid positioning mechanism, which by employing automation control, to facilitate operation, that even an unexperienced operator can carry out his/her work satisfactorily after a short time training.
These and other objects of the present invention are achieved by providing a precise and rapid positioning mechanism for stencil which comprising a stencil, a carrier, a plurality of pins and a plurality of positioning pins. These are a plurality of same sized pin eyes formed on both the stencil and the carrier respectively at positions facing against each other for interposing the pins therebetween to set the stencil and the carrier. Next, raising the positioning pins by air cylinder from the carrier so as to fit setting holes on the substrate into the corresponding positioning pins thereby firmly securing the substrate. Then afterwards, by imbibing the substrate with vacuum evacuation force from the carrier so as to put down the positioning pins thereby attaching the stencil together with the substrate and trans-printing a sodering pattern on the substrate.